The present invention relates to electric storage batteries, and more particularly to an arrangement for venting gases from thin metal film battery cells.
Thin metal film (TMF) battery technology provides a compact high power battery cell. Cells of this type are well known and their construction and manufacture have been described in, for example, U. S. Pat. Nos. 3,494,800; 5,045,086; 5,047,300; 5,198,313 and 5,368,961 the disclosures of which are hereby incorporated by reference. A thin metal film battery cell includes thin metal film plates sealed within a valve-regulated, sealed cell container. The cells include absorptive glass-mat (AGM) separator technology in an electrolyte starved system. The thin metal film plates are made from very thin lead film pasted on both surfaces with an active material. Plates having positive active material and plates having negative active material are spiral wound with separator material, and terminations are cast-on or soldered to the ends of the spiral roll. The roll is encapsulated in a container which is filled with electrolyte and then sealed.
When thin metal film batteries are charged, the excitation of the positive and negative active materials tends to heat the electrolytic fluid which causes some of the electrolytic fluid to change from a liquid to a gas. This gas accumulates and increases the pressure within the battery case. In extreme overcharging conditions, the accumulated gas can rupture the battery enclosure. Prior art inventions place openings in the battery enclosure to release the gas and prevent built-up pressure within the enclosure; however, the electrolyte may also exit through such openings. Thus, the present invention is directed to the venting of gases accumulated in a thin metal film battery housing while preventing electrolyte from exiting the housing.